linux-kernel - Re: [PATCH -next] MIPS: VDSO: Fix build error with binutils 2.24 and earlier

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Message-ID: <567C0E13.6000006@roeck-us.net>
Date:	Thu, 24 Dec 2015 07:24:03 -0800
From:	Guenter Roeck <linux@...ck-us.net>
To:	James Hogan <james.hogan@...tec.com>
Cc:	Ralf Baechle <ralf@...ux-mips.org>, linux-mips@...ux-mips.org,
	linux-kernel@...r.kernel.org, Qais Yousef <qais.yousef@...tec.com>
Subject: Re: [PATCH -next] MIPS: VDSO: Fix build error with binutils 2.24 and
 earlier

On 12/24/2015 04:48 AM, James Hogan wrote:
> Hi Guenter,
>
> On Wed, Dec 23, 2015 at 09:04:31PM -0800, Guenter Roeck wrote:
>> Commit 2a037f310bab ("MIPS: VDSO: Fix build error") tries to fix a build
>> error seen with binutils 2.24 and earlier. However, the fix does not work,
>> and again results in the already known build errors if the kernel is built
>> with an earlier version of binutils.
>>
>> CC      arch/mips/vdso/gettimeofday.o
>> /tmp/ccnOVbHT.s: Assembler messages:
>> /tmp/ccnOVbHT.s:50: Error: can't resolve `_start' {*UND* section} - `L0 {.text section}
>> /tmp/ccnOVbHT.s:374: Error: can't resolve `_start' {*UND* section} - `L0 {.text section}
>> scripts/Makefile.build:258: recipe for target 'arch/mips/vdso/gettimeofday.o' failed
>> make[2]: *** [arch/mips/vdso/gettimeofday.o] Error 1
>>
>> Fixes: 2a037f310bab ("MIPS: VDSO: Fix build error")
>> Cc: Qais Yousef <qais.yousef@...tec.com>
>> Signed-off-by: Guenter Roeck <linux@...ck-us.net>
>> ---
>> Tested with binutils 2.25 and 2.22.
>>
>>   arch/mips/vdso/Makefile | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/arch/mips/vdso/Makefile b/arch/mips/vdso/Makefile
>> index 018f8c7b94f2..14568900fc1d 100644
>> --- a/arch/mips/vdso/Makefile
>> +++ b/arch/mips/vdso/Makefile
>> @@ -26,7 +26,7 @@ aflags-vdso := $(ccflags-vdso) \
>>   # the comments on that file.
>>   #
>>   ifndef CONFIG_CPU_MIPSR6
>> -  ifeq ($(call ld-ifversion, -lt, 22500000, y),)
>> +  ifeq ($(call ld-ifversion, -lt, 22500000, y),y)
>
> I agree this is semantically correct, but there is something more evil
> going on here.
>
> Originally the check was version <= 2.24
> Qais' patch changed it to version >= 2.25 (intending version < 2.25)
> Your patch changes it to version < 2.25
>
> I think the reason this fixed the problem for Qais is actually that he
> probably had a similar toolchain version to what I'm using:
>
> GNU ld (Codescape GNU Tools 2015.06-05 for MIPS MTI Linux) 2.24.90
>

My toolchains are yocto 1.3 (2.22) and yocto 2.0 (2.25).

> ./scripts/ld-version.sh does this:
>
> print a[1]*10000000 + a[2]*100000 + a[3]*10000 + a[4]*100 + a[5];
>
> which changes that version number into:
>   20000000
> +  2400000
> +   900000 = 23300000
>
> I.e. it doesn't expect a[3] to be >= 10.
>
> Should we do something like this (increase multipliers on a[1] and
> a[2])?:
>
> diff --git a/scripts/ld-version.sh b/scripts/ld-version.sh
> index 198580d245e0..0b67edc5bc6f 100755
> --- a/scripts/ld-version.sh
> +++ b/scripts/ld-version.sh
> @@ -3,6 +3,6 @@
>   	{
>   	gsub(".*)", "");
>   	split($1,a, ".");
> -	print a[1]*10000000 + a[2]*100000 + a[3]*10000 + a[4]*100 + a[5];
> +	print a[1]*100000000 + a[2]*1000000 + a[3]*10000 + a[4]*100 + a[5];
>   	exit
>   	}
>
> which gives 2.24.90 => 224900000.
>
Yes, that makes sense, and from your description will be necessary.

Thanks,
Guenter

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